Perspective drafting machine



-2 1951 c. c. FOS'VI'ER f 2,565,724

PERSPECTIVE DRAFTING MACHINE Filed Feb. 5, 1945 INVENTOR. CLA/R C. FOSTER (I 8W +M F IG. 3 ATTORNEYS.

tween such pivot axis and pivot 24 form a triangle. Also it may be considered that the line of arm extended beyond pivot 30, the portionof control link 3 intermediate its pivot 30 and the axis of bolt 34', and a line: alignment with arm 22 between the axis of bolt 34 and the line of arm [0 extended form a second triangle. These two triangles are similar. The control toward link 23. The mechanism enabling such adjustment to be made, is shown best in Figure 3.

A saddle or slide 33 is guided for movement along the upper strap of control link 3. This saddle has in it a threaded hole through which bolt 34, about which blocks 3| pivot, may be screwed into endwise engagement with the control link. A locking disk 35 secured to a lock nut and to the bolt may be rotated to effect such 1 clamping action between the link and slide. When it is desired to change the distance bemechanism, including pulleys l5 and 26, and

cable 32, maintains link 23 parallel to arm [0, making the angle between control link 3 and link 23 equal to thefopposite angle between control link 3 and the line of arm I0 extended to the left in Figure 1; also, the angles of these triangles formed by the intersecting control link and arm 22 are equal. It follows, therefore, that the sides of such triangles are proportional.

By virtue of the similarity of the triangles mentioned the ratio between the portions into which link 3 is divided by the axis of bolt 34 will be equal to the ratio between the length of link 23 and the intercept on the line of arm Ill between pivot 30 and the intersection of lines in alignment with arm [0 and arm 22. Through whatever position straightedge 2 may be shifted over the board such intersection will remain stationary since the length of link 23 is fixed. Consequently the intersection of the lines of arms l0 and 22 defines thevanishing point for which the machine is set, toward which straight: edge 2 will always be directed, which is the requirement for perspective illustration.

As shown best in Figures 2, link 3 is preferably of double construction, including upper and lower straps or bands between which the pulleys l5 and 26 are received. This control link, in turn, is supported in cantilever .fashion by its pivot 30 being mounted in a bracket 16 carried by the end of arm I0, Link 23 and arm 22 are in turn supported by control link 3. evident, therefore, that. any angular adjustment in the position of arm I0 about its pivot II will carry bodily with it the straightedge control mechanism described. In order to shift the location of the vanishing point angularly about such pivot, therefore, it is merely necessary to loosen wing nut l4 and to rotate sector l2 to the extent desired. This sector may bear a scale graduated in degrees and cooperating with a suitable index mark on base H], to form a protractor head indicatingthe angular disposition of arm 10. Alternatively the scale may be provided on the base and the index mark placed on the sector. 1 Since the two triangles mentioned above are similar, the ratio of the parts into which the axis of bolt 34 divides control link 3 determines the ratio of all sides of the similar triangles. Because the eifective lengthof link 23 is fixed, the spacing between the vanishin point and pivot 30 may be altered by shifting the pivot axis defined by bolt 34 along link. 3. A shift of such pivot axis toward arm l0 will movethe vanishing point closer to pivot 30, whereas itcan be moved away from such pivot by shifting bolt 34 It will be tween pivot and the vanishing point, disk will be rotated in a direction to release the bolt 34'from the link, whereupon slide 33 may be shifted along the link to any desired degree.

A pointer 36, carried by saddle 33 and cooperating with a scale 31 arranged lengthwise of link 3 will indicate the proportionality into which bolt 34 divides the control link. This scale, as shown" in Figure 4, may be graduated in units of length representing thedistance between pivot 30 and the vanishing point. The divisions of the scale representing ashift of the vanishing point through a unit distance will not be uniform, but,

as is evident from Figure 4, the graduations will be increasingly close together toward pivot 25 because of the great change in proportionality which is effected by a slight increase in the angles within the triangles mentioned at opposite'sides of the intersection of arm 22 and link 3 as bolt 34 approaches pivot 25.

As previously stated, the length of link 23 is always fixed. Also, in any adjusted position of ill is immaterial which end of this arm is movable,

or whether both are movable lengthwise of the arm. Since pivot 24 preferably connects one end of arm 22 in definite relationship to link 23, however, the other end of arm 22 must be movable relative to control link 3 to change the effective length of such arm.

Preferably arm 22 is formed as a hollow channel memberhaving inturned flanges 21 which are 'engageable with rollers 38 carried by opposite ends of generally parallel resilient bands 39. These bands are secured centrally to pivot blocks 3| which are recessed to embrace bolt 34. The resilience of such bands both presses the rollers 38 against flanges 21 and also holds the blocks 31 against bolt 34. Such interconnection enables arm 22 to be mounted fully above the composite control link3, as shown in Figure 2. Moreover the combined lengths of control link 3 and link by the end of arm 22. These hinge parts are interconnected by a removable bolt 29. Such hinge parts are formed so thatwhen they are assembled as shown insolid lines in Figure 1 ,the upperedge of straightedge 2 seen in Fig. 1

. will be aligned withj'th e" center line of arm 22'.

I fbolt 29 is removed" and bracket 2| "is shifted'to' accepts assemble its hinge part in the opposite eccentric position with hinge part 28 the straightedge I will be disposed in the broken line position shown in Figure l with its lower edge in that figure" aligned with the center line of arm 22. In either position of adjustment bracket 2|,- web 20,

straightedge 2 may be swung upward about the hinge to overlie arm 22 in inoperative position, removing the scale from the drawing board sur face. I

' I claim as my invention:

1-; A perspective drafting machine comprising a straightedge, a straightedge arm supporting said straightedge, a mounting arm forsaid straightedge arm located at one side thereof, and control mechanism interconnecting said mount ifng'arm and said straightedge arm, including a link connected to said straightedge arm and cated at the side thereof opposite said mounting" arm, means operable to maintain said link always parallel to said mounting arm, and a control link interconnecting said mounting arm and said first link and connected therebetween to said straightedge arm, and operable to maintain said straightedge directed at the vanishing point in various positions relative to said mounting arm.

2. A perspective drafting machine comprising supporting means, a wheel fixed on said supporting means, a control link pivoted for swinging about the axis of said wheel, a second link pivotally connected to said control link remote from said wheel, a second wheel fixed to said second link coaxially with the pivotal connection between said two links, means interconnecting said two Wheels and operable to preserve corresponding angular relationship thereof, to'maintain the direction of said second link constant in various swung positions of said control link, a straightedge, and a straightedge arm supporting said straightedge, pivotally connected to said second link, and pivotally connected to said control link intermediate said Wheels for swinging relative thereto corresponding to swinging of said control link relative to said'supporting means While maintaining said straightedge always directed at the vanishing point.

3. A perspective drafting machine comprising supporting means, a wheel fixed on said supporting means, a control link pivoted for swinging about the axis of said wheel, a second link pivotally connected to said control link remote from said wheel, a second wheel fixed to said sec ond link coaxially with the pivotal connection between said two links, means interconnecting said two wheels and operable to preserve corresponding angular relationship thereof, to maintain the direction of said second link constant in various swung positions of said control link, a straightedge, a straightedge arm supporting said straightedge, pivotally connected tosaid second link, and pivotally connected to said" control link intermediate said wheels for swinging relative thereto corresponding to swinging of saidcontrol link relative to said supporting means while maintaining said straightedge always directed at the vanishing point, and means operable to shift the position of the pivotal connection between said straightedge arm and said con-' trol link for altering the location of the vanishing point.

V 4.- A perspective drafting machine comprising a mounting arm, a control link pivotally connected thereto, a wheel fixed relative to said mounting arm concentrically with the pivot axis of said control link, a second link pivoted upon the end or said control linklremote from said mounting arm, a second-wheel fixed to said sec:- ond link coaxially with the pivotal connection between said two links, belt means interconnect ing said two wheels and operable to preserve cor responding angular relationship thereof, to main-' tainsaid second link parallel to said mounting in variousswung positions of said control link, a straightedge, and a straightedge arm sup= porting 'said straightedge, pivotally connected to said second link, and pivotally and slidably con-f nected to said control link intermediate said wheels for swinging relative thereto correspond ing to swinging of said control link relative to said mounting arman'd for-lengthwise movement relative to said control link, to maintain said straight edge directed toward the vanishing point in allits positions.

5. The perspective drafting machine as defined incla'im- 4, and means supporting the mounting arm for swinging, thereby effecting bodily move ment of the straightedge swung through an angle corresponding to the angle of swing of the mount-: ing arm, to adjust angularly the position of the vanishing point toward which the straightedge is directed.

' 6 A perspective drafting machine as defined in claim- 4, and a slide'pivotally connected to the straightedge arm and slidably engaged with the control link for adjustment therealong to vary the distance between the vanishing point and the pivotal connection of the control link to the mounting arm, v

7. A perspective drafting machine comprising a moiint'ing arm, a control link above said mount-' ing arm, pivotally connected thereto and meme: ing spaced upper and lower members, a wheel fixed relative to said mounting arm concentrl cally with the pivot axis of said control link and received between the upper and lower members thereof, a second link pivoted upon the end of said control link remote from said mounting arm, a second wheel fixed to said second link coaxially with the pivotal connection between said two Ii'nks'and' received between the upper and lower members-of said control link, belt means interconnecting said two wheels and operable to preserve corresponding angular relationship therec'if, to maintain said second link parallel to said mounting arm in various swung positions of said control link, a straightedge, and a straightedge arm' supporting said straightedge above said control link and pivotally connected to said two links for swinging relative thereto to opposite sides of said mounting armcorresponding to swinging of said control link relative to said mounting arm, to maintain said straightedge directed toward the vanishing point in all its positions at each side of said mounting arm.

8. A perspective drafting machine comprisinga straightedge, an arm supporting said straightedge, mounting means for said arm, and control mechanisminterconnecting said mounting means andsaid ,arm for swinging said arm relative to said mounting means, such control mechanism includinga control link pivoted at one end on saidmounting means for swinging across said mounting means from one side thereof to the other, a reference link pivotally connected at one end to said arm, means pivotally interconnecting the opposite end of said reference link to the swinging end of said control link for swinging of the interconnected ends of the two links across said arm from one side thereof to the other during swinging of said control link across said mounting means, pivot means carried byrsaid; control link between the ends thereof, a'longitudinal slide connection-between said arm and said latter pivot means guiding said arm for sliding across said control link during swinging of said control link at opposite sides of andacross said mountingmeans, and reference link'orient ing means interconnecting said mounting means and said reference link to maintain the latter constantly oriented relative to said mounting means during said swinging of said control link, thereby maintainingv the straightedge directed toward a selected vanishing point in its various swung positions relative-to said mounting means.

9. The perspective drafting machine defined in claim 8, and guide means on the control link for adjusting the position of the pivot means lengthwise thereof.

10. A perspective drafting machine comprising astraightedge, anarm supporting said straigh edge, mounting means for said straightedge, and control mechanism interconnecting said arm and said mounting means for swinging of said arm relative to said mounting means while maintaining said straightedge directed at thevanishing point in all its swung positions, and including a link connected to said arm, a control link, means guiding said control link for swinging thereof across said mounting means from one side thereof to the other through a range, said control link crossing said arm and being pivotally connected thereto for swinging of said arm and longitudinal sliding thereof relative to said control link, pivot means interconnecting said first link and said control link at a location more remote from said mounting means than its crossing with said am, and means interconnecting said mounting means and said first link for controlling orientation thereof. I

-11. In a perspective drafting machine, a straightedge, an arm supporting said straightedge, pivot means guiding said arm for swinging, means controlling swinging of said arm about said pivot means to dispose said straightedge, in various swung positions of said arm, directed toward a given vanishing point, and means, including a coupling element carried by the end of said arm and a complemental coupling element carried by the end of said straightedge, interconnecting said straightedge and said arm, said arm-carried coupling element having first straightedge sup-porting means disposed eccentrically of said arm and second straightedge supporting means disposed eccentrically of said arm to the side thereof opposite said first straightedge supporting means, and said complemental straightedge coupling element having means selectively engageable with said first straightedge supporting means to dispose an edge of said straightedge in precise alignmentwith the vanishing point with the straightedge disposed bodily on one side of the line of alignment, and further engageable with said second straightedge supporting means to dispose an edge of said straightedge in precise alignment with the vanishing point when the straightedge is disposed bodily on the opposite side of such line of alignment.

12. A perspective drafting machine comprising a mounting member, a control link pivotally connected to said mounting member for swinging freely through a substantial angular range, asecond link pivotally connected to said control link at, a location spaced; lengthwise on such control link from its pivot on said-mounting member, to swing relative to the control link into and to either side of parallelism with said control link in a plane parallel to the latter's plane of swing relative to said mounting member and also thereby to be carried by said control link to be swung bodily thereby, control means including coordinated elements fixed to said sec" ond link and said mounting member, respectively:

and maintaining said second link in fixed angular relation to said mounting member in various bodily swung positions of said second link carried by such control link, a straightedge arm, first means pivotally connecting said straightedge arm to said second link, second means spaced lengthwise of said straightedge arm from its first pivot and pivotally connecting said straightedge arm to said control link, said first and second pivotal connecting means supporting said straightedge arm in offset relation to said control link and second link on the same side of both thereof to swing through parallelism with such control link and second link without interference therefrom, one of said first and second pivotal connecting means including slide means permitting lengthwise sliding of said straightedge' bodily carried by said straightedge arm.

13. The perspective drafting machine defined in claim 12, and means operable to adjust length- WiS8 'Of the control link the location thereon of the second means pivotally connecting the straightedge arm thereto.

CLAIR. C. FOSTER.

REFERENCES CITED The following references are of record in the file of this patent: V UNITED STATES PATENTS Number Name Date 189,620 Fuller Apr. 17, 1877 335,853 Thompson Feb. 9, 1886 497,147 Urich May 9, 1893 838,799 Nagle Dec. 18, 1906 1,286,525 Buck Dec. 3, 1918 1,586,067 Christian l May 25, 1926 1,685,486 Graham Sept. 25, 1928 1,826,338 Acherberg Oct. 6, 1931 2,049,302 Little July 28, 1936 2,364,153 MacCleod Dec. 5, 1944 2,413,376 Pomeroy Dec. 31, 1946 FOREIGN PATENTS Number Country Date 1,553 Great Britain. 1871 15,679 Great Britain 1894 291,015

Great Britain Nov. 1, 1928 

